Natural Cycles would have screwed me
Full disclosure: I am a Natural Cycles user and love the whole concept, but I do NOT fully trust the algorithm for birth control. And here's why:
Women are actually infertile most of the month, so the "effectiveness" comes from helping you avoid unprotected sex in the 6 day fertile window each cycle.
The data that Natural Cycles collects from you (Basal Body Temperature if it’s taken with an oral thermometer, or an algorithm-adjusted skin temperature change if you use a wearable like an Oura ring) is important to understand first.
Body temperature rises AFTER ovulation. This is thanks to the progesterone that gets produced when an egg is ovulated.
So logically speaking, ovulation can only be confirmed after it’s already happened. It does not help you predict it’s coming, or when it’s about to happen.
^^understanding that is key.
So what allows you to predict ovulation is coming, and indicates you’re in your fertile window NOW?
Cervical mucus.
And unfortunately, Natural Cycles does not take cervical mucus patterns into account, nor does it allow for algorithm adjustments based on this primary fertile sign you would be seeing.
So while NC is great at closing the fertile window (thanks to BBT), it lacks the fertile sign information that opens the fertile window - which is where the REAL risk of unintended pregnancy lies.
The NC app uses a predictive algorithm to give you “red” days that indicate the start of your fertile window, and I don’t doubt it’s a sophisticated algorithm.
But it’s not your body. And your body signs will always be superior.
In the fertility awareness world, we reject what we call “rhythm method thinking” - which is where you use past cycle information to predict your current and future cycles. And that’s a problem, because we know it’s not how biology works. (and it’s why the rhythm method is not so hot for birth control).
Fertility awareness = using your body’s real-time fertile signs to understand “is today a fertile day? Yes or no.” EACH day. Zero reliance on old patterns, because that can fail you.
Yet the nature of a predictive algorithm is that it’s literally fed past information to generate future data.
While it’s quite a robust prediction, if you have an irregular cycle you’re more likely to fall victim to an error. Plus, even perfectly healthy and regular cycles STILL don’t ovulate on the same day each month.
My message will always be: your body knows best, and it’s your right (and duty, honestly) to learn how to read it.
As much as I love the idea of empowerment behind this app, it's unfortunately reinforcing the archaic ideas that 1.) we're too dumb to handle our own fertile signs ourselves, or 2.) it's just far too risky to trust our own body fully.
And I reject both those ideas. You can absolutely learn a natural method of birth control that is 99% effective (with proper training) that you can TRUST.
Want a solid understanding of what that looks like?
This video will give you a great foundation of how this works.
Written by Michelle Snyder, MS. 3/19/2025The information on this website is provided for educational purposes only and should not be treated as medical or spiritual advice. WTT Nutrition makes no guarantees regarding the information provided or how products may work for any individual. If you suffer from a health condition, you should consult your health care practitioner for medical advice before introducing any new products into your health care regimen. For more information, please read our terms and conditions.